I hope I have shown here that the portcullis system in the Ante Chamber would be extremely ineffective as a 'security system' to secure the King's Chamber as it effectively 'invites' people into the chamber and provides them with a mechanism to raise the granite portcullis stones.
But from the evidence that others have posted here, it seems there are other matters to consider, primarily among these is the extreme 'wear' of the Great Step (now 'repaired'). Was this in some way related to the portcullis mechanism? It's possible.
As you can see - and as others have pointed out earlier in this thread - there is a 'V' shaped groove in the middle of the Great Step. To my mind this may not actually be the result of wear (well, some of it might) but that it was deliberately created as a channel or guide for ropes.
Notice also in the image below, the parallel slots along each side of the Grand Gallery, spaced at regular intervals:
These slots may also be a clue as to the role of the portcullis system of the Ante Chamber. Let me explain.
In Jean-Pierre Houdin's 'Internal Ramp Theory' he speculates that the Grand Gallery once contained a large, wooden cradle that would act as a counter-weight for the raising of the seriously heavy granite beams and slabs of the King's Chamber and its 'relieving chambers'. Some of these granite blocks weigh around 70 tons. Houdin imagines that the wooden cradle would rest at the top of the Grand Gallery and be loaded up as a counter weight (perhaps using bags of sand or granite balls). The brace holding the cradle in place would then be removed, allowing the weighted cradle counter-weight to slip down the Grand Gallery thereby hauling up the heavy granite slabs (see images below from Houdin's presentation):
Once at the bottom of the Grand Gallery, the cradle counter-weight would be unloaded of its sacks of sand or granite balls and the lighter wooden cradle then returned to the top of the Grand Gallery.
Now, the question is (and I do not believe this has been answered by Houdin's theory), how was the cradle returned to the top of the Grand Gallery? This would have been a significant weight in its own right, even without the weight of the sand.
Perhaps the answer to this problem was the Portcullis System. Perhaps the Portcullis System of the Ante Chamber was actually a mechanism used to haul the Cradle in the Grand Gallery back to the top of the gallery, ready to be loaded again and make its next descent. Obviously the Ante Chamber mechanism could only haul the Cradle a short distance at a time up the gallery due to the short distance that the portcullis slabs could fall. But at each stop the cradle would be braced or locked in place using wooden chocks placed into the slots on either side of the gallery. The granite portcullis slabs in the Ante Chamber would then be raised again (using the granite leaf counter-weight in this chamber), and haul the Cradle up another short distance to the next slot where it would be braced and so on until the cradle was returned to the top of the gallery.
Obviously the Cradle would be attached to ropes and these ropes would run through the 'V' shape in the Great Step as in the image below:
Post Edited (29-Jun-12 16:11)